To further improve integration degrees of semiconductors such as of a large scale integration (LSI), finer patterns are made during productions of semiconductors, and currently the smallest pattern size is 100 nm or smaller.
Formations of such fine patterns in semiconductor devices have been realized by shortening wavelength of light from a light source of exposure devices and improving resist materials. Currently, formations of fine patterns have been performed by a liquid immersion lithography, in which exposure is performed through water with a light source that emits argon fluoride (ArF) excimer laser light having a wavelength of 193 nm, and as a resist material used for such lithography, various ArF resist materials using acrylic resins as a base have been developed. Moreover, as a lithography technique of the next generation, an extreme ultraviolet (EUV) lithography using soft X rays having a wavelength of 13.5 nm as a light source has been studied, and therefore it is obvious that a pattern size will continue to be reduced, e.g. 30 nm or smaller, from now on.
As the pattern size is made smaller as mentioned above, unevenness of a pattern width becomes more significant, which may adversely affect performances of a resulting device.
To solve the aforementioned problems, there have attempts to optimize exposure devices and resist materials for use. However, sufficient results have not been provided. Moreover, improvements of exposure devices and resist materials take a lot of time and cost.
Accordingly, various countermeasures have been studied and provided in process conditions.
For example, there is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2007-213013 a method for improving LWR in which a resist pattern is treated with an aqueous solution containing an ionic surfactant during a rinsing process after a developing process so as to dissolve the roughness of the resist pattern at the same time as reducing defects (e.g. defects including residues, and deformation of the pattern) caused by the developing process (see JP-A No. 2007-213013).
Moreover, another method is disclosed in JP-A No. 2010-49247, and in this method an organic coating material, to which a low molecular acidic compound containing a carboxyl group, is applied to a resist pattern that has been developed, and the coating material is then removed to thereby improve LWR as well as sliming the resist pattern (see JP-A No. 2010-49247).
However, any of these methods has a problem that a desirable resist pattern size cannot be obtained as the improvement of LWR is realized by removing a surface of a resist pattern by processing. Moreover, these methods have a problem that LWR may be potentially worsened.
The present inventors have disclosed a resist pattern thickening material that enables precise processing by swelling (thickening) the resist pattern (see Japanese Patent (JP-B) No. 3633595, and JP-A No. 2006-259692).
In the case where a resist pattern is subjected to a thickening process using such resist pattern thickening material, however, a size of the resist pattern is largely changed. Therefore, it is not suitable for a material for improving LWR, which desirably improves LWR of a resist pattern, without changing a size of the resist pattern more than necessary.
Accordingly, it is a current situation that a resist pattern improving material, a method for forming a resist pattern, and a method for producing a semiconductor device, that can improve LWR of a resist pattern without changing a size thereof more than necessary.